Apparatus and methods for reducing embolization during treatment of carotid artery disease

ABSTRACT

Methods and apparatus are provided for removing emboli during an angioplasty, stenting or surgical procedure comprising a catheter having an occlusion element, an aspiration lumen, and a blood outlet port in communication with the lumen, a guide wire having a balloon, a venous return catheter with a blood inlet port, and tubing that couples the blood outlet port to the blood inlet port. Apparatus is also provided for occluding the external carotid artery to prevent reversal of flow into the internal carotid artery. The pressure differential between the artery and the vein provides reverse flow through the artery, thereby flushing emboli. A blood filter may optionally be included in-line with the tubing to filter emboli from blood reperfused into the patient.

REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of application Ser.No. 09/333,074, now U.S. Pat. No. 6,206,868, filed Jun. 14, 1999, whichis a continuation- in-part of International Application PCT/US99/05469,filed Mar. 12, 1999, which is a continuation-in-part of U.S. patentapplication Ser. No. 09/078,263, filed May 13, 1998.

FIELD OF THE INVENTION

This invention relates to apparatus and methods for protecting againstembolization during vascular interventions, such as carotid arteryangioplasty and endarterectomy. More particularly, the apparatus andmethods of the present invention induce substantially continuousretrograde flow through the internal carotid artery during treatmentduring an interventional procedure, without significant blood loss.

BACKGROUND OF THE INVENTION

Carotid artery stenoses typically manifest in the common carotid artery,internal carotid artery or external carotid artery as a pathologicnarrowing of the vascular wall, for example, caused by the deposition ofplaque, that inhibits normal blood flow. Endarterectomy, an opensurgical procedure, traditionally has been used to treat such stenosisof the carotid artery.

An important problem encountered in carotid artery surgery is thatemboli may be formed during the course of the procedure, and theseemboli can rapidly pass into the cerebral vasculature and cause ischemicstroke.

In view of the trauma and long recuperation times generally associatedwith open surgical procedures, considerable interest has arisen in theendovascular treatment of carotid artery stenosis. In particular,widespread interest has arisen in transforming interventional techniquesdeveloped for treating coronary artery disease, such as angioplasty andstenting, for use in the carotid arteries. Such endovascular treatments,however, are especially prone to the formation of emboli.

Such emboli may be created, for example, when an interventionalinstrument, such as a guide wire or angioplasty balloon, is forcefullypassed into or through the stenosis, as well as after dilatation anddeflation of the angioplasty balloon or stent deployment. Because suchinstruments are advanced into the carotid artery in the same directionas blood flow, emboli generated by operation of the instruments arecarried directly into the brain by antegrade blood flow.

Stroke rates after carotid artery stenting have widely varied indifferent clinical series, from as low as 4.4% to as high as 30%. Onereview of carotid artery stenting including data from twenty-four majorinterventional centers in Europe, North America, South America and Asia,had a combined initial failure and combined mortality/stroke rate ofmore than 7%. Cognitive studies and reports of intellectual changesafter carotid artery stenting indicate that embolization is a commonevent causing subclinical cerebral damage.

Several previously known apparatus and methods attempt to remove emboliformed during endovascular procedures by trapping or suctioning theemboli out of the vessel of interest. These previously known systems,however, provide less than optimal solutions to the problems ofeffectively removing emboli.

Solano et al. U.S. Pat. No. 4,921,478 describes cerebral angioplastymethods and devices wherein two concentric shafts are coupled at adistal end to a distally-facing funnel-shaped balloon. A lumen of theinnermost shaft communicates with an opening in the funnel-shapedballoon at the distal end, and is open to atmospheric pressure at theproximal end. In use, the funnel-shaped balloon is deployed proximally(in the direction of flow) of a stenosis, occluding antegrade flow. Anangioplasty balloon catheter is passed through the innermost lumen andinto the stenosis, and then inflated to dilate the stenosis. The patentstates that when the angioplasty balloon is deflated, a pressuredifferential between atmospheric pressure and the blood distal to theangioplasty balloon causes a reversal of flow in the vessel that flushesany emboli created by the angioplasty balloon through the lumen of theinnermost catheter.

While a seemingly elegant solution to the problem of emboli removal,several drawbacks of the device and methods described in the Solano etal. patent seem to have lead to abandonment of that approach. Chiefamong these problems is the inability of that system to generate flowreversal during placement of the guide wire and the angioplasty balloonacross the stenosis. Because flow reversal does not occur until afterdeflation of the angioplasty balloon, there is a substantial risk thatany emboli created during placement of the angioplasty balloon willtravel too far downstream to be captured by the subsequent flowreversal. It is expected that this problem is further compounded becauseonly a relatively small volume of blood is removed by the pressuredifferential induced after deflation of the angioplasty balloon.

Applicant has determined another drawback of the method described in theSolano patent: deployment of the funnel-shaped balloon in the commoncarotid artery (“CCA”) causes reversal of flow from the external carotidartery (“ECA”) into the internal carotid artery (“ICA”), due to thelower flow impedance of the ICA. Consequently, when a guide wire orinterventional instrument is passed across a lesion in either the ECA orICA, emboli dislodged from the stenosis are introduced into the bloodflow and carried into the cerebral vasculature via the ICA.

The insufficient flow drawback identified for the system of the Solanopatent is believed to have prevented development of a commercialembodiment of the similar system described in EP Publication No. 0 427429. EP Publication No. 0 427 429 describes use of a separate balloon toocclude the ECA prior to crossing the lesion in the ICA. However, likeSolano, that publication discloses that flow reversal occurs only whenthe dilatation balloon in the ICA is deflated.

Chapter 46 of Interventional Neuroradiology: strategies and practicaltechniques (J. J. Connors & J. Wojak, 1999), published by Saunders ofPhiladelphia, Pa., describes using a coaxial balloon angioplasty systemfor patients having with proximal ICA stenoses. In particular, a small,deflated occlusion balloon on a wire is introduced into the origin ofthe ECA, and a guide catheter with a deflated occlusion balloon ispositioned in the CCA just proximal to the origin of the ECA. A dilationcatheter is advanced through a lumen of the guide catheter and dilatedto disrupt the stenosis. Before deflation of the dilation catheter, theocclusion balloons on the guide catheter and in the ECA are inflated toblock antegrade blood flow to the brain. The dilation balloon then isdeflated, the dilation catheter is removed, and blood is aspirated fromthe ICA to remove emboli.

Applicant has determined that cerebral damage still may result from theforegoing previously known procedure, which is similar to that describedin EP Publication No. 0 427 429, except that the ICA is occluded priorto the ECA. Consequently, both of these previously known systems andmethods suffer from the same drawback—the inability to generate flowreversal at sufficiently high volumes during placement of the guide wireand dilation catheter across the stenosis. Both methods entail asubstantial risk that any emboli created during placement of the balloonwill travel too far downstream to be captured by the flow reversal.

Applicants note, irrespective of the method of aspiration employed withthe method described in the foregoing Internvetional Neuroradiologyarticle, substantial drawbacks are attendant. If, for example, naturalaspiration is used (i.e., induced by the pressure gradient between theatmosphere and the artery), then only a relatively small volume of bloodis expected to be removed by the pressure differential induced afterdeflation of the angioplasty balloon. If, on the other hand, an externalpump is utilized, retrieval of these downstream emboli may require aflow rate that cannot be sustained for more than a few seconds,resulting insufficient removal of emboli.

Furthermore, with the dilation balloon in position, the occlusionballoons are not inflated until after inflation of the dilation balloon.Microemboli generated during advancement of the dilation catheter intothe stenosed segment may therefore be carried by retrograde blood flowinto the brain before dilation, occlusion, and aspiration are evenattempted.

A still further drawback of both the device in EP Publication No. 0 427429 and the Internvetional Neuroradiology device is that, if they areused for placing a stent in the ICA instead of for ICA angioplasty, thestent often extends beyond the bifurcation between the ECA and the ICA.The occlusion balloon placed by guide wire in the ECA may snag the stentduring retrieval. Emergency surgery may then be required to remove theballoon.

Imran U.S. Pat. No. 5,833,650 describes a system for treating stenosesthat comprises three concentric shafts. The outermost shaft includes aproximal balloon at its distal end that is deployed proximal of astenosis to occlude antegrade blood flow. A suction pump then drawssuction through a lumen in the outermost shaft to cause a reversal offlow in the vessel while the innermost shaft is passed across thestenosis. Once located distal to the stenosis, a distal balloon on theinnermost shaft is deployed to occlude flow distal to the stenosis.Autologous blood taken from a femoral artery using an extracorporealblood pump is infused through a central lumen of the innermost catheterto provide continued antegrade blood flow distal to the distal balloon.The third concentric shaft, which includes an angioplasty balloon, isthen advanced through the annulus between the innermost and outermostcatheters to dilate the stenosis.

Like the device of the Solano patent, the device of the Imran patentappears to suffer the drawback of potentially dislodging emboli that arecarried into the cerebral vasculature. In particular, once the distalballoon of Imran's innermost shaft is deployed, flow reversal in thevasculature distal to the distal balloon ceases, and the blood perfusedthrough the central lumen of the innermost shaft establishes antegradeflow. Importantly, if emboli are generated during deployment of thedistal balloon, those emboli will be carried by the perfused blooddirectly into the cerebral vasculature, and again pose a risk ofischemic stroke. Moreover, there is some evidence that reperfusion ofblood under pressure through a small diameter catheter may contribute tohemolysis and possible dislodgment of emboli.

In applicant's co-pending U.S. patent application Ser. No. 09/333,074,filed Jun. 14, 1999, which is incorporated herein by reference,applicant described the use of external suction to induce regionalreversal of flow. That application further described that intermittentlyinduced regional flow reversal overcomes the drawbacks ofnaturally-aspirated systems such as described hereinabove. However, theuse of external suction may in some instances result in flow rates thatare too high to be sustained for more than a few seconds. In addition,continuous use of an external pump may result in excessive blood loss,requiring infusion of non-autologous blood and/or saline that causeshemodilution, reduced blood pressure, or raise related safety issues.

In view of these drawbacks of the previously known emboli removalsystems, it would be desirable to provide methods and apparatus forremoving emboli from within the carotid arteries during interventionalprocedures, such as angioplasty or carotid stenting, that reduce therisk that emboli are carried into the cerebral vasculature.

It also would be desirable to provide methods and apparatus for removingemboli from within the carotid arteries during interventionalprocedures, such as angioplasty or carotid stenting, that providesubstantially continuous low retrograde blood flow from the treatmentzone, thereby reducing the risk that emboli are carried into thecerebral vasculature.

It further would be desirable to provide emboli removal methods andapparatus that prevent the development of reverse flow from the ECA andantegrade into the ICA once the CCA has been occluded, thereby enhancingthe likelihood that emboli generated by a surgical or interventionalprocedure are effectively removed from the vessel.

It still further would be desirable to provide an occlusion balloon on aguide wire for placement in the ECA during stenting of the ICA thatmitigates the risk of snagging the stent during removal.

It also would be desirable to provide methods and apparatus for removingemboli during a carotid stenting procedure that enable filtering ofemboli and reduced blood loss.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of this invention to providemethods and apparatus for removing emboli from within the carotidarteries during interventional procedures, such as angioplasty orcarotid stenting, that reduce the risk that emboli are carried into thecerebral vasculature.

It also is an object of the present invention to provide methods andapparatus for removing emboli from within the carotid arteries duringinterventional procedures, such as angioplasty or carotid stenting, thatprovide substantially continuous low retrograde blood flow from thetreatment zone, thereby reducing the risk that emboli are carried intothe cerebral vasculature.

It is another object of the present invention to provide emboli removalmethods and apparatus that prevent the development of reverse flowbetween the ECA and ICA once the common carotid artery has beenoccluded, thereby enhancing the likelihood that emboli generated by asurgical or interventional procedure are effectively removed from thevessel.

It is a further object of this invention to provide methods andapparatus for an occlusion balloon on a guide wire for placement in theECA during stenting of the ICA that mitigates the risk of snagging thestent during removal.

It is yet another object of the present invention to provide methods andapparatus for removing emboli during a carotid stenting procedure thatenable filtering of emboli and reduced blood loss.

The foregoing objects of the present invention are accomplished byproviding interventional apparatus comprising an arterial catheter, anocclusion balloon disposed on a guide wire, a venous return catheter,and optionally a blood filter. The arterial catheter has proximal anddistal ends, an aspiration lumen extending therebetween, an occlusionelement disposed on the distal end, and a hemostatic port and bloodoutlet port disposed on the proximal end that communicate with theaspiration lumen. The aspiration lumen is sized so that aninterventional instrument, e.g., an angioplasty catheter or stentdelivery system, may be readily advanced therethrough to the site of astenosis in either the ECA (proximal to the balloon) or the ICA.

In accordance with the principles of the present invention, the arterialcatheter is disposed in the CCA proximal of the ICA/ECA bifurcation, theocclusion balloon on the guide wire is disposed in the ECA to occludeflow reversal from the ECA to the ICA, and the blood outlet port of thearterial catheter is coupled to the venous return catheter, with orwithout the blood filter disposed therebetween. Higher arterial thanvenous pressure, especially during diastole, permits substantiallycontinuous flow reversal in the ICA during the procedure (other thanwhen a dilatation balloon is inflated), thereby flushing bloodcontaining emboli from the vessel. The blood is filtered and reperfusedinto the body through the venous return catheter.

Methods of using the apparatus of the present invention are alsoprovided.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the invention, its nature and various advantageswill be more apparent from the accompanying drawings and the followingdetailed description of the preferred embodiments, in which:

FIGS. 1A and 1B are schematic views of previously known emboliprotection systems;

FIG. 2 is a schematic view of the emboli protection system of thepresent invention;

FIGS. 3A-3D are, respectively, a schematic view, and detailed side andsectional views of the distal end of an interventional device of thepresent invention;

FIGS. 4A and 4B are views of the distal end of an alternativeinterventional device suitable for use in the system of the presentinvention; and

FIGS. 5A-5D illustrate a method of using the system of FIG. 3 inaccordance with the principles of the present invention;

FIGS. 6A-6B are, respectively, a schematic view and a cross-sectionalview of an alternative embodiment of the device of FIGS. 3;

FIGS. 7A-7B are, respectively, a schematic view of an alternativeembodiment of the guide wire balloon elements of the device of FIGS. 3,and a method of using the alternative embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1A and 1B, drawbacks of previously known emboliremoval catheters are described with reference to performingpercutaneous angioplasty of stenosis S in common carotid artery CCA.

With respect to FIG. 1A, drawbacks associated with naturally-aspiratedemboli removal systems, such as described in the above-mentioned patentto Solano and European Patent Publication, are described. No flowreversal is induced by those systems until after balloon 10 ofangioplasty catheter 11 first is passed across the stenosis, inflated,and then deflated. However, applicant has determined that once member 15of emboli removal catheter 16 is inflated, flow within the ECA reversesand provides antegrade flow into the ICA, due to the lower hemodynamicresistance of the ICA. Consequently, emboli E generated while passingguide wire 20 or catheter 11 across stenosis S may be carriedirretrievably into the cerebral vasculature—before flow in the vessel isreversed and directed into the aspiration lumen of emboli removalcatheter 16 by opening the proximal end of the aspiration lumen toatmospheric pressure. Furthermore, natural-aspiration may not remove anadequate volume of blood to retrieve even those emboli that have not yetbeen carried all the way into the cerebral vasculature.

In FIG. 1B, system 17 described in the above-mentioned patent to Imranis shown. As described hereinabove, deployment of distal balloon 18, andejection of blood out of the distal end of the inner catheter, maydislodge emboli from the vessel wall distal to balloon 18. Theintroduction of antegrade flow through inner catheter 19 is expectedonly to exacerbate the problem by pushing the emboli further into thecerebral vasculature. Thus, while the use of positive suction in theImran system may remove emboli located in the confined treatment fielddefined by the proximal and distal balloons, such suction is notexpected to provide any benefit for emboli dislodged distal of distalballoon 18.

Referring now to FIG. 2, apparatus and methods of the present inventionare described. Apparatus 30 comprises catheter 31 having an aspirationlumen and occlusion element 32, and guide wire 35 having inflatableballoon 36 disposed on its distal end. In accordance with the principlesof the present invention, antegrade blood flow is stopped when bothocclusion element 32 in the CCA and inflatable balloon 36 are deployed.Furthermore, the aspiration lumen of catheter 31 is connected to avenous return catheter (described hereinbelow), disposed, for example,in the patient's femoral vein. In this manner a substantially continuousflow of blood is induced between the treatment site and the patient'svenous vasculature. Because flow through the artery is towards catheter31, any emboli dislodged by advancing a guide wire or angioplastycatheter 33 across stenosis S causes the emboli to be aspirated bycatheter 31.

Unlike the previously known naturally-aspirated systems, the presentinvention provides substantially continuous retrograde blood flowthrough eh ICA while preventing blood from flowing retrograde in the ECAand antegrade into the ICA, thereby preventing emboli from being carriedinto the cerebral vasculature. Because the apparatus and methods of thepresent invention “recycle” emboli-laden blood from the arterialcatheter through the blood filter and to the venous return catheter, thepatient experiences significantly less blood loss.

Referring now to FIG. 3A, embolic protection apparatus 40 constructed inaccordance with the principles of the present invention is described.Apparatus 40 comprises arterial catheter 41, guide wire 45, venousreturn line 52, tubing 49 and optional blood filter 50.

Catheter 41 includes distal occlusion element 42, proximal hemostaticport 43, e.g., a Touhy-Borst connector, inflation port 44, and bloodoutlet port 48. Guide wire 45 includes balloon 46 that is inflated viainflation port 47. Tubing 49 couples blood outlet port 48 to filter 50and blood inlet port 51 of venous return line 52.

Guide wire 45 and balloon 46 are configured to pass through hemostaticport 43 and the aspiration lumen of catheter 41 (see FIGS. 3C and 3D),so that the balloon may be advanced into and occlude the ECA. Port 43and the aspiration lumen of catheter 41 are sized to permit additionalinterventional devices, such as angioplasty balloon catheters,atherectomy devices and stent delivery systems to be advanced throughthe aspiration lumen when guide wire 45 is deployed.

Guide wire 45 preferably comprises a small diameter flexible shafthaving an inflation lumen that couples inflatable balloon 46 toinflation port 47. Inflatable balloon 46 preferably comprises acompliant material, such as described hereinabove with respect toocclusion element 42 of emboli removal catheter 41.

Venous return line 52 includes hemostatic port 53, blood inlet port 51and a lumen that communicates with ports 53 and 51 and tip 54. Venousreturn line 52 may be constructed in a manner per se known for venousintroducer catheters. Tubing 49 may comprise a suitable length of abiocompatible material, such as silicone. Alternatively, tubing 49 maybe omitted and blood outlet port 48 of catheter 41 and blood inlet port51 of venous return line 52 may be lengthened to engage either end offilter 50 or each other.

With respect to FIGS. 3B and 3C, distal occlusion element 42 comprisesexpandable bell or pear-shaped balloon 55. In accordance withmanufacturing techniques which are known in the art, balloon 55comprises a compliant material, such as polyurethane, latex orpolyisoprene which has variable thickness along its length to provide abell-shape when inflated. Balloon 55 is affixed to distal end 56 ofcatheter 41, for example, by gluing or a melt-bond, so that opening 57in balloon 55 leads into aspiration lumen 58 of catheter 41. Balloon 55preferably is wrapped and heat treated during manufacture so that distalportion 59 of the balloon extends beyond the distal end of catheter 41and provides an atraumatic tip or bumper for the catheter.

As shown in FIG. 3D, catheter 41 preferably comprises inner layer 60 oflow-friction material, such as polytetrafluoroethylene (“PTFE”), coveredwith a layer of flat stainless steel wire braid 61 and polymer cover 62(e.g., polyurethane, polyethylene, or PEBAX). Inflation lumen 63 isdisposed within polymer cover 62 and couples inflation port 44 toballoon 55. In a preferred embodiment of catheter 41, the diameter oflumen 58 is 7 Fr, and the outer diameter of the catheter isapproximately 9 Fr.

Referring now to FIGS. 4A and 4B, an alternative embodiment of occlusionelement 42 of the system of FIG. 3A is described. In FIGS. 4A and 4B,occlusion element 42 of emboli removal catheter 41 comprisesself-expanding wire basket 65 covered with elastomeric polymer 66, suchas latex, polyurethane or polyisoprene. Alternatively, a tightly knitself-expanding wire mesh may be used, with or without an elastomericcovering.

Catheter 41 is surrounded by movable sheath 67. Catheter 41 is insertedtransluminally with sheath 67 in a distalmost position, and after basket65 has been determined to be in a desired position proximal to astenosis, sheath 67 is retracted proximally to cause basket 65 todeploy. Upon completion of the procedure, basket 65 is again collapsedwithin sheath 67 by moving the sheath to its distalmost position.Operation of the system of FIG. 3A using the emboli removal catheter ofFIGS. 4A and 4B is similar to that described hereinbelow for FIGS.5A-5D, except that the occlusion element self-expands when sheath 67 isretracted, rather than by infusing an inflation medium to balloon 55.

Referring now to FIGS. 5A-5D, use of the apparatus of FIGS. 3 inaccordance with the methods of the present invention is described. InFIGS. 5, stenosis S is located in internal carotid artery ICA above thebifurcation between the internal carotid artery ICA and the externalcarotid artery ECA. In a first step, catheter 41 is inserted, eitherpercutaneously and transluminally or via a surgical cut-down, to aposition proximal of stenosis S, without causing guide wire 45 to crossthe stenosis. Balloon 55 of distal occlusion element 42 is theninflated, preferably with a radiopaque contrast solution, via inflationport 44. As seen in FIG. 5A, this creates reversal of flow from theexternal carotid artery ECA into the internal carotid artery ICA.

Venous return line 52 then is introduced into the patient's femoralvein, either percutaneously or via a surgical cut-down. Filter 50 isthen coupled between blood outlet port 48 of catheter 41 and blood inletport 51 of venous return line 52 using tubing 49, and any air is removedfrom the line. Once this circuit is closed, negative pressure in thevenous catheter during diastole will establish a low rate continuousflow of blood through aspiration lumen 58 of catheter 41, as seen inFIG. 5B, to the patient's vein via venous return line 52.

This low rate continuous flow due to the difference between venouspressure and arterial pressure will continue throughout theinterventional procedure. Specifically, blood passes through aspirationlumen 58 and blood outlet port 48 of catheter 41, through biocompatibletubing 49 to filter 50, and into blood inlet port 51 of venous returnline 52, where it is reperfused into the remote vein. Filtered embolicollect in filter 50 and may be studied and characterized uponcompletion of the procedure.

Continuous blood flow (except during inflation of any dilatationinstruments) with reperfusion in accordance with the present inventionprovides efficient emboli removal with significantly reduced blood loss.Alternatively, filter 50 may be omitted, in which case emboli removedfrom the arterial side will be introduced into the venous side, andeventually captured in the lungs. Because of a low incidence of septaldefects, which could permit such emboli to cross-over to the leftventricle, the use of filter 50 is preferred.

Referring to FIG. 5C, with balloon 55 of occlusion element 42 inflatedand a retrograde flow established in the ICA, guide wire 45 and balloon46 are advanced through aspiration lumen 58. When balloon 46 is disposedwithin the ECA, as determined, e.g., using a fluoroscope and aradiopaque inflation medium injected into balloon 46, balloon 46 isinflated. Occlusion of the ECA prevents the development of reverse flowin the ECA from causing antegrade flow in the ICA. Anotherinterventional instrument, such as conventional angioplasty ballooncatheter 71 having balloon 72, is loaded through hemostatic port 43 andaspiration lumen 58 and positioned within the stenosis. Hemostatic port43 is closed and instrument 71 is actuated to disrupt the plaque formingstenosis S.

As seen in FIG. 5D, upon completion of the angioplasty portion of theprocedure using catheter 71, balloon 72 is deflated. Throughout theprocedure, except when the dilatation balloon is fully inflated, thepressure differential between the blood in the ICA and the venouspressure causes blood in ICA to flow in a retrograde direction in theICA into aspiration lumen 58 of emboli removal catheter 41, therebyflushing any emboli from the vessel. The blood is filtered andreperfused into the patient's vein.

Optionally, increased volumetric blood flow through the extracorporealcircuit may by achieved by attaching an external pump, such as a rollerpump, to tubing 49. If deemed beneficial, the external pump may be usedin conjunction with device 40 at any point during the interventionalprocedure. Instrument 71, guide wire 45, emboli removal catheter 41, andvenous return line 52 are then removed from the patient, completing theprocedure.

As set forth above, the method of the present invention protects againstembolization, first, by preventing the reversal of blood flow from theECA to the ICA when distal occlusion element 42 is inflated, and second,by providing continuous, low volume blood flow from the carotid arteryto the remote vein in order to filter and flush any emboli from thevessel and blood stream. Advantageously, the method of the presentinvention permits emboli to be removed with little blood loss, becausethe blood is filtered and reperfused into the patient. Furthermore,continuous removal of blood containing emboli prevents emboli frommigrating too far downstream for aspiration.

Referring now to FIGS. 6, apparatus 140 constructed in accordance withthe present invention is described. Apparatus 140 is an alternativeembodiment of apparatus 40 described hereinabove and comprises arterialcatheter 141 having distal occlusion element 142, proximal hemostaticport 143, inflation port 144 and blood outlet port 148. Guide wire 145includes balloon 146 that is inflated via inflation port 147.Biocompatible tubing 149 couples blood outlet port 148 to filter 150 andto blood inlet port 151 of venous return line 152. Arterial catheter141, guide wire 145, venous return line 152 and tubing 149 areconstructed as described hereinabove, except as noted below.

Guide wire 145 and balloon 146 are configured to pass through guide wirelumen 164 of catheter 141 (see FIG. 6B), so that the balloon may beadvanced into and occlude the ECA. Additionally, catheter 141 comprisesaspiration lumen 158 which is sized to permit interventional devices,such as angioplasty balloon catheters, atherectomy devices and stentdelivery systems to be advanced through port 143 and the aspirationlumen. As shown in FIG. 6B, the key difference between catheters 41 and141 lies in the method of advancing the guide wire through the catheter:guide wire 45 is advanced through the aspiration lumen of catheter 41,whereas guide wire 145 is advanced through separate guide wire lumen 164of catheter 141.

Catheter 141 preferably is constructed from inner layer 160 oflow-friction material, such as polytetrafluoroethylene (“PTFE”), coveredwith a layer of flat stainless steel wire braid 161, and polymer cover162 (e.g., polyurethane, polyethylene, or PEBAX). Inflation lumen 163 isdisposed within polymer cover 162 and couples inflation port 144 toocclusion element 142. Guide wire lumen 164 also is disposed withinpolymer cover 142, and is sized to permit guide wire 145 and balloon 146to pass therethrough. In a preferred embodiment of catheter 141, thediameter of inflation lumen 163 is 0.014″, the diameter of guide wirelumen 164 is 0.020″, and the diameter of lumen 158 is 7 Fr. To retain anouter catheter diameter in the preferred embodiment of approximately 9Fr., the thickness of the catheter wall varies around the circumferencefrom a maximum of 0.026″ at the location of guide wire lumen 164 to aminimum of 0.005″ 180 degrees away.

Referring now to FIGS. 7, an alternative embodiment of the guide wireocclusion apparatus of the present invention is described. Occlusionapparatus 200 comprises guide wire 201, occlusion balloon 202, inflationlumen 203, and wedge 204. Wedge 204 may comprise a resilient material,such as a polymer or resilient wire, and reduces the risk that balloon202 will snag on a stent that extends beyond the bifurcation of the ICAand ECA.

For the reasons described hereinabove, it is desirable when performing astenting procedure in the ICA to occlude the ECA, to prevent flowreversal from the ECA and into the ICA. Accordingly, an occlusionballoon on a guide wire is placed in the ECA and inflated to block thatartery. A stent then may be placed in the ICA to ensure proper bloodflow to the ICA. It is often desirable, however, for such stents toextend beyond the bifurcation between the ECA and the ICA. Consequently,when the occlusion balloon on the guide wire is deflated and withdrawnfrom the ECA, there is a risk that the balloon may snag the stent. Insuch cases, emergency surgery is often required to remove the balloon.

Referring now to FIG. 7B, occlusion apparatus 200 is illustrativelyshown in conjunction with catheter 41. Stent S extends beyond thebifurcation between the ECA and the ICA and into the CCA. Balloon 202 isdeflated and positioned for retrieval. Because balloon 202 is disposedon guide wire 201 instead of a traditional, larger diameter ballooncatheter, its cross-sectional diameter is significantly reduced, andthus the risk that the balloon will snag on stent S is reduced.Resilient wedge 204 further reduces this risk by urging the balloonoutward away from the stent during retrieval of guide wire 201 andballoon 202. Alternatively, a separate sheath may be advanced over guidewire 201 and occlusion balloon 202 to surround those components, andtherefore reduce the risk that the occlusion balloon or guide wire willsnag the stent.

While preferred illustrative embodiments of the invention are describedabove, it will be apparent to one skilled in the art that variouschanges and modifications may be made. The appended claims are intendedto cover all such changes and modifications that fall within the truespirit and scope of the invention.

What is claimed is:
 1. Apparatus for removing emboli from the cerebral vasculature, the apparatus comprising: a catheter having proximal and distal ends, a lumen extending therethrough, and a blood outlet port in communication with the lumen, the catheter having an outer diameter sufficient to permit the catheter to be disposed in the cerebral vasculature; a pear-shaped inflatable occlusion element disposed on the distal end of the catheter, the occlusion element having a contracted state suitable for transluminal insertion and an expanded state wherein the occlusion element occludes antegrade flow in the vessel, the occlusion element extending beyond the distal end of the catheter in the expanded state to form a tapered entrance to the lumen; a venous return catheter having a proximal end with an inlet port and a distal end with an outlet port, and a lumen extending therebetween, the blood outlet port coupled to the inlet port of the venous return catheter; and a wire having a distal end and a balloon disposed on the distal end, wherein the wire and balloon are sized to pass through the lumen of the catheter.
 2. The apparatus of claim 1 further comprising a blood filter coupled between the blood outlet port and the inlet port of the venous return catheter.
 3. The apparatus of claim 1 wherein the occlusion element has a wall thickness that varies along the length of the occlusion element.
 4. The apparatus of claim 3 wherein a portion of the pear-shaped inflatable occlusion element extends beyond the distal end of the catheter in the contracted position and forms an atraumatic bumper.
 5. The apparatus of claim 1 wherein the catheter further comprises a second lumen through which the wire and inflatable balloon may be inserted.
 6. The apparatus of claim 1 further comprising a roller pump that engages the venous return catheter to assist in drawing blood through the catheter and in reperfusing blood via the venous return catheter.
 7. The apparatus of claim 1 further comprising a resilient wedge affixed to the wire proximal of the balloon to reduce snagging of the balloon following a stenting procedure.
 8. Apparatus for removing emboli from the cerebral vasculature, the apparatus comprising: a catheter having proximal and distal ends, a lumen extending therethrough, a non-stick tubular member, a layer of wire braid disposed surrounding the non-stick tubular member, a layer of thermoplastic polymer disposed on the layer of wire braid, and a blood outlet port in communication with the lumen, the catheter having an outer diameter sufficient to permit the catheter to be disposed in the cerebral vasculature; a pear-shaped inflatable occlusion element disposed on the distal end of the catheter, the occlusion element having a contracted state suitable for transluminal insertion and an expanded state wherein the occlusion element occludes antegrade flow in the vessel, the occlusion element extending beyond the distal end of the catheter in the expanded state to form a tapered entrance to the lumen; a venous return catheter having a proximal end with an inlet port and a distal end with an outlet port, and a lumen extending therebetween, the blood outlet port coupled to the inlet port of the venous return catheter.
 9. The apparatus of claim 8 further comprising a wire having a distal end and a balloon disposed on the distal end, wherein the wire and balloon are sized to pass through the lumen of the catheter.
 10. The apparatus of claim 9 wherein the catheter further comprises a second lumen through which the wire and inflatable balloon may be inserted.
 11. The apparatus of claim 8 further comprising a blood filter coupled between the blood outlet port and the inlet port of the venous return catheter.
 12. The apparatus of claim 8 wherein the occlusion element has a wall thickness that varies along the length of the occlusion element.
 13. The apparatus of claim 12 wherein a portion of the pear-shaped inflatable occlusion element extends beyond the distal end of the catheter in the contracted position and forms an atraumatic bumper.
 14. The apparatus of claim 8 further comprising a roller pump that engages the venous return catheter to assist in drawing blood through the catheter and in reperfusing blood via the venous return catheter.
 15. A method for removing emboli from a vessel within the cerebral vasculature, the method comprising: providing a catheter having proximal and distal ends, a lumen extending therethrough, an inflatable, pear-shaped occlusion element disposed on the distal end, a hemostatic port coupled to the lumen, and a blood outlet port coupled to the lumen, the occlusion element extending beyond the distal end of the catheter and forming a tapered entrance to the lumen when the occlusion element is expanded; providing a venous return catheter having proximal end with an inlet port, a distal end with an outlet port, and a lumen extending therebetween; inserting the distal end of the catheter into the cerebral vasculature to a position proximal to a treatment site; inserting the distal end of the venous return catheter into a remote vein; coupling the blood outlet port to the inlet port of the venous return catheter; expanding the occlusion element to occlude antegrade flow through the vessel so that the occlusion element forms a tapered entrance to the lumen; and causing blood to flow between the blood outlet port and the inlet port of the venous return catheter to induce reverse flow in, and remove emboli from, the vessel.
 16. The method of claim 15 further comprising: providing a blood filter; and coupling the blood filter in fluid communication between the blood outlet port and the inlet port of the venous return catheter.
 17. The method of claim 15 further comprising: providing a wire having a balloon; while flow is reversed in the vessel, advancing the balloon of the wire into the patient's external carotid artery; inflating the balloon of the wire to prevent reverse flow from the external carotid artery from entering the internal carotid artery.
 18. The method of claim wherein advancing the balloon of the wire into the patient's external carotid artery comprises advancing the balloon through a separate lumen of the catheter.
 19. The method of claim 15 further comprising, while causing blood to flow between the blood outlet port and the inlet port, performing an interventional procedure with an interventional instrument inserted through the hemostatic port.
 20. The method of claim 19 wherein performing an interventional procedure with an interventional instrument comprises delivering a stent within the vessel and the wire further comprises a resilient wedge, the method further comprising urging the resilient wedge against the stent during removal of the wire and balloon.
 21. The method of claim 15 further comprising: providing a roller pump; engaging the roller pump with the venous return catheter; and actuating the pump to increase a rate of flow of blood between the blood outlet port and the inlet port. 